By the Bev. T. PerUns, M.A. 177 



shown that it underlies the Portland beds, which themselves underlie 

 the wealdeu formations there, and reaches a greater thickness than 

 in Dorset, having been probably deposited in a deeper sea. 



Above the Kimeridge clay lies the Portland sand, and above this 

 the Portland stone, which has so high a reputation as a building 

 stone. It is quarried in the Isle of Portland, and also at Chilmark, 

 near Fonthill, near Tisbury, and at Chicksgrove ; at the last-named 

 place the beds are level, whereas at the other three they are much 

 inclined. Not all the Portland beds are useful as building stone, 

 but some of the stone from these local quarries is excellent and 

 it was from them that the stone of which Salisbury Cathedral 

 is built was obtained. 



Throughout these liassic and oolitic times the land had been 

 gradually sinking, but, after the deposition of the Portland beds a 

 gradual upheaval took place, which, though probably not very 

 marked, threw the oolitic strata out of the horizontal plane, giving 

 them a slight dip to the east, and also once more uniting the islands 

 of the west to the continent. These islands now took the form of 

 mountains rising above the plain of the upper oolites, across which 

 from unknown sources a mighty river ran, which had its delta in 

 the area now occupied by the south-eastern part of what is now 

 England, by part of the English Channel and by the north-eastern 

 part of France. In the Vale of Wardour in the west, in the" 

 neighbourhood of Boulogne in the east, in the Isle of Wight in 

 the south, and in Buckinghamshire in the north, these estuarine 

 deposits are found. If we measure the distance east and west we 

 find it two hundred miles, and if we measure the distance north and 

 south we find it one hundred miles. But there is every reason to 

 suppose that these estuarine and fresh water deposits extended still 

 further, and probably the area of the delta was over thirty thousand 

 square miles — not far short in size of the delta of the Ganges and 

 Brahmaputra combined. So that we may safely say that this old 

 river of wealden times was equal in size to some of the largest rivers 

 of the modern world. To the west of the plain through which it 

 flowed rose the hills of Devon, separated from the hills of Wales by 

 a broad plain — now the Bristol Channel — the Mendip Hills lay 



